Abstract Background: Estimating intraoperative blood loss can be a difficult task, especially when blood is mostly absorbed by gauze. In this study, we haveprovidedanimprovedmethodforestimatingbloodthatwasabsorbedbygauze. Objectives: To developaguidethatmedicalstaffcanusetoestimatebloodlossthatwasabsorbedbysurgicalgauze. Materials and Methods: Aclinical experiment was conducted using expired blood and commonsizes of surgical gauze to create a realistic stain of absorbed blood inthegauze. Differentpercentagesof stainingwerephotographedtocreateananalogueforthe amountof bloodabsorbedbythegauze. Results: A visual analogue was created to aid the estimation of blood absorbed by the gauze. The absorptive capacity of different gauzesizeswasdeterminedwhenthegauzewasdrippingwithblood. Theamountof reductioninabsorptionwasalsodetermined whenthegauzewaswettedwithnormalsalinebeforeuse. Conclusions: Theuseofavisualanaloguewillincreasetheaccuracyofbloodlossestimationanddecreasetheconsequencesrelated to overorunderestimationof bloodloss. Keywords: BloodLoss,Surgical,EstimationTechniques,Absorption 1. Background Visual estimation is the most common method to estimate intraoperative blood loss, but it is not the most accurate (1). Estimating blood loss might be difficult, especially if most of the blood is absorbed by surgical gauze andnotcollectedinthesuctionbottle(2). Althoughmany methodsfor estimation are available, e.g., the gravimetric method (weighing of the pre-and post-procedure gauze), mostarenotinroutineuseeitherduetotheirunavailability or time-consuming nature during surgical procedures (1). In the literature, there are only a few tools to improve visual estimation (1, 3). Thus, improving the visual estimationmethodiscrucialforaccurateestimationof blood loss. 2. Objectives Theaimofthisstudyistodevelopananaloguethatcan beeasilyrememberedbythestaffandusedtoestimateany bloodabsorbedbysurgicalgauze. 3. MaterialsandMethods A cross-sectional study was carried out to determine the absorptive capacity of surgical gauze along with a case-control study to determinetheabsorptivecapacityof gauzewettedwithsalineandsupersaturatedgauzeascompared to the drygauze. Three different sizes of commonly used surgical gauze (10 × 10 cm, 30 × 30 cm, and 45 × 45 cm) were tested for their absorptive capacity and used to reconstruct the analogue. Using personal protective equipment, a measured amount of expired whole blood (tested negative for blood-borne diseases) was spilled into a bowl (simulating operative bleeding). Then, a resident was asked to dry the blood. The blood spill was gradually increased (Figure 1). The increment in blood spill was 3 ml in the 10 × 10 gauze, 10 mL in the 30 × 30 gauze, and 40 mLinthe45×45gauze.Thestainsthatresultedfromthis spill were photographedforthevisualguide. After the gauze testing was complete, four patterns wereselected for eachgauzetoconstructthevisualguide. Each pattern represented 25%, 50%, 75%, and 100% saturation.
Then,supersaturationof thegauzewasdeterminedby addingmorebloodtothe100% saturatedgauze. Supersaturationwasdeterminedbytheinabilityof thegauzetoabsorbextrabloodfromthebowlandbeginningtodrip(Figure2). Figure2. Supersaturationof GauzeWithBlood This wasrepeatedwithpiecesof wetgauze. Wettingof the gauzepieces wasachievedbydippingtheminnormal saline andsqueezingouttheexcesssaline. Approval from the hospital research and ethics committeewasobtainedpriortothestudy,andproperdisposal of thebloodandgauzewasfollowed.
4. Results Thebelowguideshowsthepatternof stainingandabsorptive capacity of each gauze (Figure 3). Wetting of the gauze decreased the absorptive capacity to 25% (dry 12 mL vs. wet 9mL)inthe10×10cm,30% (dry100mLvs. wet70 mL)inthe30×30cm,and25% (dry160mLvs.wet140ml) in the 45 ×45cmgauze. Supersaturation of the gauze increased the absorptive capacity to 25% (12 mL vs. 15 mL) in the 10×10cm,30% (100mLvs. 130mL)inthe30×30cm, and25% (160mLvs. 200mL)inthe45×45cmgauze. 5. Discussion Apatient losing bloodduringanysurgeryisaconcern forboththesurgeonandanesthetist. Preciseestimationof blood loss is crucial because underestimation may lead to significant complications, and overestimation and unnecessary transfusion may increase complications and mortality (4, 5). There are many methods for intraoperative blood loss estimation, e.g., gravimetric, photometry, and visual estimation, but the most used method is visual estimation. Other methods are not widely used due to their unavailability, impracticality, or time consumption, e.g., gravimetric method, as the gauze must be weighed preand post-use (1, 5). Although visual estimation is a commonly used method, it is the least accurate (1, 2). The discrepancy in visual estimation is not only between the actualbloodlossandtheestimatedamountbutalsobetween the anesthesiologists who tend to overestimate and the surgeonswhotendtounderestimatebloodloss(6,7). This discrepancy may lead to a conflict with transfusion decisionsasanesthesiologistsdependontheclinicaljudgment
astheonlytriggerforintraoperativetransfusion(8,9). The estimation becomes more challenging when the surgeon uses saline-wetted gauze, as this decreases the absorptive capacity of thegauze,orwhenthegauzeissupersaturated anddripping(Figure4). Many investigators are trying to devise new methods for anaccuratedeterminationof bloodloss. Teachingstaff how to estimate blood loss has shown to be effective in increasing the accuracy of visual estimation (1, 10-12). In mostof thepublishedarticlesonimprovingvisualestimation, a clinical scenario or pictures of blood stains have been usedtotest or teach the targeted people; these studies have shown that visual analogues and scenarios are a goodmethodforteaching(1,10-12). Assessmentof thestaff beforeteachingshowedthattheiryearsof experience(resident vs. attending estimation) did not improve the estimation accuracy (10, 12, 13). This fact raised the need for a methodthatwouldincrease the estimation ability in all staff rankings, experienced or not. Although a significant reduction in error wasshownafterteachinginthesestudies, none of them showed a perfect estimation of blood loss. This means that any tool that improves the visual estimation will haveamarginof error(1,10-13). In the experiment, expired whole blood was used to simulateatruebloodstain,andarandompatternof staining was also done by simulating a realistic scenario of blood loss (Figure 1). All of this effort is to avoid pitfalls that may happen due to the use of a colored solution or
dipping the gauze directly into the blood. In addition, we havetestedtheabsorptivecapacityof gauzewhenitiswetted with saline or dripping with blood because these situations have never been tested before in other studies and have asignificant effect on the amountof bloodabsorbed bythegauze. Therearesomelimitationstoourstudy. First,asshown bypreviousstudies,therewillbesomeerrorinestimation even when using such an analogue. Thus, this analogue will decrease the error but will not eliminate it. Second, the analogue was constructed by testing a certain type of gauze that is commonlyusedinhospitals. If another type or size of gauze is used, this analogue may be inaccurate for use(14). 5.1. Conclusion Careshouldbetakenwhenestimatingbloodlossbyvisual estimation. Theuseof clinicalguidesimprovesthevisual estimation and decreases the error when estimating bloodthathasbeenabsorbedbysurgicalgauze. Acknowledgments WeacknowledgetheKingFahadhospitalresearchand ethicalcommitteefortheirhelpandguidancethroughout the studyprocessandpublication.
Footnote Authors’ Contribution: Dr. Emran Algadiem: concept, design,definitionofintellectualcontent,literaturesearch, data acquisition, data analysis, manuscript preparation, manuscriptediting, manuscriptreview, guarantor; Dr. Abdulmohsen Aleisa: concept, design, manuscript preparation, manuscript editing, manuscript review; Dr. Huda Alsubaie: literature search, clinical studies, experimental studies, manuscript review; Dr. Noora Radhi Buhlaiqah: literature search, clinical studies, experimental studies, manuscript review; Dr. Jihad Algadeeb: literature search, clinical studies, experimental studies, manuscript review; Hussain Alsneini: literature search, clinical studies, experimentalstudies, manuscriptrev